In the prior art, cobalt silicide electrodes have been suggested for commercial use as electrode metallization contacts to silicon in semiconductor transistor devices, particularly insulated gate field effect transistor devices. When a cobalt silicide electrode metallization contact to silicon is initially made at a temperature below about 550.degree. C., such an electrode is essentially formed as cobalt monosilicide (CoSi); and if, as ordinarily desired during further processing thereafter, the temperature of the device being fabricated is subsequently raised to a value above about 600.degree. C., then the cobalt monosilicide is converted into cobalt disilicide (CoSi.sub.2) and this conversion produces an increase in the volume of the cobalt silicide. Such an increase in volume can cause undesirable strains unless there is sufficient empty space (such as that provided by an exposed surface of the cobalt silicide) into which the cobalt disilicide can expand.
If a contact to silicon is initially formed directly as cobalt disilicide by heating cobalt metal in contact with the silicon to a temperature above about 550.degree. C. or 600.degree. C., then the subsequent need to raise the processing temperature to a value above 900.degree. C.--for such purposes as gettering of impurities, or annealing of damage, or flowing of phosphosilicate glass (P-glass)--causes undesirable grain growth in the cobalt disilicide as well as undesirable migration of silicon from the underlying source and drain regions to the cobalt disilicide electrode, which migration deteriorates the transistor operation. Furthermore, heating of the cobalt disilicide to temperatures above about 900.degree. C. increases the resistance of the cobalt disilicide--which is especially undesirable for the gate electrode--probably because of intermixing of the cobalt disilicide with silicon. In addition, at temperatures above about 600.degree. C., pure cobalt itself reacts with the silicon dioxide ordinarily present on the wafer in regions removed from the cobalt silicide electrode, whereby undesirable compounds are formed that are difficult to remove differentially, i.e., while leaving intact the cobalt silicide as ordinarily desired in patterning the structure by differential etching. Also, above about 600.degree. C., cobalt has a tendency to draw, by diffusion into itself, any nearby silicon or phosphorus, which undesirably lengthens the gate electrode and deteriorates any phosphorus doped glass (P-glass). It would, therefore, be desirable to have a method of forming cobalt disilicide electrode contacts to silicon which alleviates these problems.